1. Technical Field
The present invention generally relates to semiconductor wafers and, more particularly, to a protective coating and adhesive for use in conjunction with semiconductor wafer dry etch applications.
2. Discussion
Semiconductor wafers are currently being used in a myriad of applications. In order to prepare the semiconductor wafer for such applications, it is often necessary to provide electrical access to the circuitry on the front side of the wafer by forming via holes through the wafer. The via holes provide electrical continuity from the backside to the front side of the wafer.
Advanced semiconductor devices often perform via hole etching using plasma techniques, where the processing temperature range is 50-250xc2x0 C. In order to accomplish such etching, a protective coating is required on the front side of the wafer to provide mechanical protection. Since via hole etching is generally performed on thin wafers (25-250 xcexcm), the wafer is mounted onto a substrate with an adhesive. The wafer can now be properly maneuvered and safely handled during the wafer thinning and via hole etch processes. However, the protective coating and mounting adhesive must be easy to remove after the wafer thinning and via hole etch process.
According to the prior art, photoresists are commonly used as a protective coating to protect the front side circuitry of the wafer during the wafer thinning and via hole etch process. However, commonly used photoresists are inadequate protective coatings during higher temperature wafer thinning or via hole etching processes since they decompose at high temperatures. Furthermore, conventional adhesives, used to bond the wafer to the substrate such as waxes and epoxy are also inadequate, since the waxes often melt and epoxy-based adhesives are extremely difficult to remove after processing at high temperatures.
In view of the foregoing, there is a need in the art for a protective coating and adhesive which are compatible with high temperature semiconductor wafer thinning and via hole etching processes.
The above and other objects are provided by a method of backside processing a semiconductor wafer including applying a polymer based protective coating on the wafer, depositing a barrier layer on the protective coating, and coating the barrier layer with a thermoplastic based adhesive or using a single layer coating that embodies the characteristics of a protective coating and an adhesive layer. Thereafter, the wafer is bonded to a substrate and then lapped and polished to a desired thickness and patterned with an etch mask. A 50-250xc2x0 C. plasma etching process is then used to etch via holes in the wafer. After etching and subsequent backside processing, the adhesive layer is dissolved in an organic solvent to separate the wafer from the substrate. Thereafter, the protective coating is dissolved with an organic solvent to separate the barrier layer from the finished wafer. If a single layer coating is used, it is dissolved with an organic solvent to separate the finished wafer from the substrate.